JP5729526B1 - Elastic wave device - Google Patents

Abstract

Provided is an acoustic wave device in which a leak failure in a hollow part where an acoustic wave element part faces is less likely to occur. A plurality of acoustic wave element portions having IDT electrodes are formed on the piezoelectric substrate 2, and a support layer 16 surrounding the acoustic wave element portion on the piezoelectric substrate 2 so as to form a hollow portion where each acoustic wave element portion faces. Are provided, and a cover member is laminated on the support layer 16 to form each hollow portion facing the acoustic wave element portion. The support layer 16 includes a first support layer 17 and a second support layer. The first support layer 17 is along the outer peripheral edge of the piezoelectric substrate 2, and the second support layer 18 is located in a region surrounded by the first support layer 17. Each acoustic wave element part is provided around the acoustic wave element part so as to have a hollow part, and a hollow path 19 is provided between the first support layer 17 and the second support layer 18. In addition, the acoustic wave device 1 is provided so that the hollow path 19 communicates with at least two hollow portions.

Description

  The present invention relates to an acoustic wave device in which a plurality of IDT electrodes are formed on a piezoelectric substrate. More specifically, the present invention relates to an acoustic wave device in which a plurality of IDT electrodes are sealed with a support layer and a cover member.

  Conventionally, various acoustic wave devices called wafer level packages (WLP) have been proposed. Patent Document 1 below discloses an example of this type of acoustic wave device. A plurality of surface acoustic wave element portions are formed on one piezoelectric substrate. Each surface acoustic wave element has at least a part of an IDT electrode. In order to seal the surface acoustic wave element portion, in Patent Document 1, a support layer is formed on the piezoelectric substrate so as to surround the surface acoustic wave element portion. And the cover member is joined on the support layer. Thereby, a hollow portion where the surface acoustic wave element portion faces is formed.

WO2009 / 116222

  In the elastic wave device described in Patent Document 1, a cover member is stacked on and bonded to a support layer. In some cases, voids were generated at the joint. For this reason, the hollow portion and the outside communicate with each other through the void, and the hermeticity of the hollow portion is lowered, and a leak failure may occur.

  An object of the present invention is to provide an elastic wave device in which the above-described leakage failure is unlikely to occur.

  An elastic wave device according to the present invention includes a piezoelectric substrate, a plurality of elastic wave element portions, a support layer, and a cover member. The plurality of acoustic wave element portions are provided on the piezoelectric substrate and have at least one IDT electrode. The support layer is disposed on the piezoelectric substrate outside the region where the elastic wave element portion is provided in order to form a hollow portion in each portion where the elastic wave element portion is provided. . The cover member is laminated on the support layer in order to seal each portion where the acoustic wave element portion is provided and form the hollow portion. In the present invention, the support layer includes a first support layer disposed along the outer peripheral edge of the piezoelectric substrate, and a second support layer disposed in a region surrounded by the first support layer. And a support layer. The second support layer is provided so as to surround a portion where the acoustic wave element portion is provided in a region surrounded by the first support layer. In the present invention, a hollow path is provided between the first support layer and the second support layer, and the hollow path is disposed so as to communicate at least two of the hollow portions.

  On the specific situation with the elastic wave apparatus concerning this invention, the opening part is provided in the said 2nd support layer so that the plane area of the said 2nd support layer may be made small.

  In another specific aspect of the acoustic wave device according to the present invention, the first support layer has a closed loop shape.

  In still another specific aspect of the acoustic wave device according to the present invention, the plurality of hollow portions are liquid-tightly sealed.

  In still another specific aspect of the acoustic wave device according to the present invention, when viewed in a plan view, the outer peripheral edge of the cover member reaches the outer peripheral edge of the piezoelectric substrate, thereby forming a wafer level package.

  According to the elastic wave device according to the present invention, the support layer has the first and second support layers, and the hollow path is provided between the first support layer and the second support layer. It becomes possible to effectively suppress the leakage failure due to the generation of voids. That is, even if a void is generated in the second support layer, only the hollow path and the hollow portion communicate with each other, and a leak failure between the outside and the hollow portion hardly occurs. In addition, since it is divided into the first support layer and the second support layer, the area of the second support layer can be reduced, and the generation of voids can also be suppressed. Therefore, a leak failure due to the generation of voids hardly occurs. Therefore, it is possible to effectively suppress a leak failure due to the generation of voids.

FIG. 1 is a schematic plan view showing a structure in which the cover member of the acoustic wave device according to the first embodiment of the present invention is removed. FIG. 2 is a partially cutaway cross-sectional view showing a main part of the acoustic wave device according to the first embodiment of the present invention. FIG. 3A is a diagram illustrating a circuit configuration of the acoustic wave device according to the first embodiment, and FIG. 3B is a plan view illustrating an example of an electrode structure of a 1-port acoustic wave resonator. FIG. 4 is a schematic plan view showing a structure in which the cover member is removed in the acoustic wave device according to the second embodiment. FIG. 5 is a schematic plan view showing a structure in which the cover member is removed in the elastic wave device of the comparative example.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1 is a schematic plan view showing a structure in which a cover member is removed in an elastic wave device according to a first embodiment of the present invention. FIG. 2 is a partially cutaway cross-sectional view showing a main part of the elastic wave device according to the first embodiment of the present invention, and FIG. 3A is a circuit diagram of the elastic wave device according to the first embodiment.

As shown in FIGS. 1 and 2, the acoustic wave device 1 includes a piezoelectric substrate 2. The piezoelectric substrate 2 is formed of a piezoelectric single crystal substrate or a piezoelectric ceramic plate such as LiTaO ₃ or LiNbO ₃ . In the present embodiment, the piezoelectric substrate 2 is a rectangular plate-shaped piezoelectric single crystal substrate.

  By configuring a plurality of acoustic wave element portions on the piezoelectric substrate 2, a duplexer is configured in the present embodiment. More specifically, a duplexer having the circuit configuration shown in FIG.

  As shown in FIG. 3A, the acoustic wave device 1 has an antenna terminal 3. A common terminal 4 is connected to the antenna terminal 3. A transmission filter 7 is configured between the common terminal 4 and the transmission terminal 5. A reception filter 8 is configured between the common terminal 4 and the pair of balanced terminals 6a and 6b.

  The transmission filter 7 has a ladder circuit configuration. That is, it has series arm resonators S1, S2, S3a, S3b, and S4 each made of an elastic wave resonator, and parallel arm resonators P1 to P4. The series arm resonators S1 to S4 and the parallel arm resonators P1 to P4 are made of a 1-port elastic wave resonator.

  The 1-port elastic wave resonator has an electrode structure shown in FIG. An IDT electrode 11 and reflectors 12 and 13 disposed on both sides of the IDT electrode 11 in the elastic wave propagation direction are formed on the piezoelectric substrate 2. Thereby, a 1-port elastic wave resonator is configured.

  Returning to FIG. 1, on the piezoelectric substrate 2, a part in which the series arm resonators S <b> 1 to S <b> 4 and the parallel arm resonators P <b> 1 to P <b> 4 are configured is schematically shown by a symbol in which X is surrounded by a rectangular frame. That is, the portions where the series arm resonators S1 to S4 and the parallel arm resonators P1 to P4 are configured are elastic wave element portions, respectively.

  Returning to FIG. 3A, in the reception filter 8, a 1-port elastic wave resonator 9 as a trap filter is connected to the common terminal 4. Between the 1-port type acoustic wave resonator 9 and the balanced terminals 6a and 6b, 3IDT type longitudinally coupled resonator type acoustic wave filter sections 14 and 15 are provided. The longitudinally coupled resonator type acoustic wave filter units 14 and 15 are connected in cascade. In the present embodiment, the reception filter 8 is a balanced filter having a pair of balanced terminals 6a and 6b. However, the reception filter may be an unbalanced filter. The longitudinally coupled resonator type acoustic wave filter unit is formed with a plurality of IDTs arranged side by side in the propagation direction of the surface acoustic wave propagating on the surface of the piezoelectric substrate 2, and reflectors are provided on both sides of the plurality of IDT groups. Just do it. For example, as a configuration having an odd number of IDT groups of 3 or more, a configuration in which the longitudinally coupled resonator type acoustic wave filter section has five IDTs may be used.

  Returning to FIG. 1, on the piezoelectric substrate 2, each part of the 1-port type acoustic wave resonator 9 and the longitudinally coupled resonator type acoustic wave filter units 14 and 15 is schematically illustrated in a shape in which X is surrounded by a frame. Will be shown. In the reception filter 8 as well, the portions where the 1-port type acoustic wave resonator 9 and the longitudinally coupled resonator type acoustic wave filter units 14 and 15 are configured are the acoustic wave element units in the present invention.

  In addition, the IDT electrode, the reflector, and the connection wiring in each of the acoustic wave element portions can be formed of an appropriate metal or alloy such as Ag, Cu, Pt, or W.

  In the acoustic wave device 1, it is necessary to provide a space for preventing the vibration of the acoustic wave element portion from being hindered. However, it is necessary to seal the space in order to suppress frequency fluctuations and improve moisture resistance.

  In the present embodiment, the support layer 16 is provided around the acoustic wave element portion so that each of the acoustic wave element portions faces the hollow portion. The support layer 16 includes a first support layer 17 and a second support layer 18.

  The support layer 16 can be formed of an appropriate insulating material. Preferably, a synthetic resin is preferably used because it can be reduced in weight and cost and can be manufactured more easily. More preferably, a photosensitive resin is used because patterning is easy. By using a photosensitive resin, patterning can be easily performed by a photolithography method or the like. Thereby, the first and second support layers 17 and 18 and the hollow path 19 described later can be easily formed.

  As the photosensitive resin, a conventionally known appropriate photosensitive resin can be used. As such a photosensitive resin, a photosensitive polyimide, a photosensitive epoxy resin, a photosensitive silicone resin, or the like can be used. Photosensitive polyimide is more desirable because it has moderate rigidity and elasticity and can perform patterning with high accuracy.

  As shown in FIG. 1, the support layer 16 is disposed in a first support layer 17 provided along the outer peripheral edge of the piezoelectric substrate 2 and a region surrounded by the first support layer 17. 2 support layers 18. The 2nd support layer 18 is provided so that the circumference | surroundings of this elastic wave element part may be surrounded so that the hollow part which each elastic wave element part may face may be comprised.

  A hollow path 19 in which no support layer exists is provided between the second support layer 18 and the first support layer 17. As a modification, in the normal direction of the surface of the piezoelectric substrate 2, a hollow support layer having a height lower than the height of the second support layer 18 and the height of the first support layer 17 is partially provided. A path 19 may be formed.

  FIG. 2 is a partially cutaway sectional view schematically showing a portion where the parallel arm resonator P3 is formed. Here, a parallel arm resonator P3 is formed as the elastic wave element portion. A hollow portion A is formed so that the IDT electrode 31 faces. That is, the hollow portion A is surrounded and formed by the second support layer 18 and the cover member 20. On the one side surface side of the piezoelectric substrate 2, the first support layer 17 is located outside the second support layer 18 through the hollow path 19. The hollow path 19 is provided so as to communicate at least two hollow portions facing the acoustic wave element portion.

  Since the support layer 16 is divided into the first support layer 17 and the second support layer 18, the area of the second support layer 18 can be reduced.

  This will be described in comparison with FIG. FIG. 5 shows an elastic wave device 101 of a comparative example in which a support layer 102 having no hollow path 19 is provided in place of the support layer 16. The elastic wave device 101 is the same as the above embodiment except that the support layer 102 is provided.

  In the elastic wave device 101 of the comparative example shown in FIG. 5, the area of the support layer 102 is large.

  On the other hand, in this embodiment, as shown in FIG. 1, the support layer 16 is divided into a first support layer 17 and a second support layer 18. The rectangular frame-shaped main body portion 17a of the first support layer 17 is connected to the via conductor forming portion 17b. The width of the main body portion 17a of the first support layer 17 is preferably 50 μm or less in order to prevent air from entering the bonding surface, and preferably 10 μm or more in order to ensure the bonding strength between the support layer 16 and the cover member 20. . In the present embodiment, the width of the main body portion 17a is 20 μm. That is, since it is divided by the hollow path 19, the area of the first support layer 17 and the area of the second support layer 18 are smaller than the area of the support layer 102 of the elastic wave device 101 of the comparative example. The width of the hollow path 19 is preferably in the range of 10 μm or more and 100 μm or less.

  Although the cover member is not illustrated in FIG. 1, in the acoustic wave device 1, the cover member 20 is laminated so as to cover the entire upper surface of the support layer 16 as illustrated in FIG. 2. The cover member 20 can be formed of an appropriate insulating material. Preferably, the cover member 20 is made of a synthetic resin. In that case, the manufacturing process can be simplified and the cost can be reduced.

  Such a synthetic resin is not particularly limited, and for example, an epoxy resin or polyimide can be used. When an epoxy resin is used, it can be cured at a temperature of about 170 ° C. to 220 ° C., for example. Therefore, the cover member 20 can be formed by heat curing and bonded onto the support layer 16 by a relatively low temperature curing process.

  By the way, joining of the cover member 20 which consists of the above synthetic resins is joined by press-contacting on the support layer 16 toward the other side from the one side of the sheet-like cover member 20 using a roller, for example. It is performed using the process to do. In this case, air may enter the joint surface between the cover member 20 and the support layer 16 to generate voids. However, in this embodiment, since the support layer 16 is divided into the first and second support layers 17 and 18, the generation of voids is suppressed. For this reason, the leak defect of the hollow part by a void can also be suppressed effectively.

  In addition, after the acoustic wave device 1 is mounted on the module substrate, the acoustic wave device 1 may be sealed with a mold resin using a transfer mode method. In this case, a large pressure is applied to the cover member 20 from the cover member 20 side to the piezoelectric substrate 2 side, and a large pressure is also applied to the joint portion between the cover portion 20 and the support layer 16. Therefore, a part of the cover member may be deformed to interfere with the IDT electrode in the hollow portion. However, in this embodiment, by providing the first support layer 17 and the second support layer 18, this deformation is suppressed by the tension of the cover member 20 generated by the deformation of the hollow path 19. Therefore, the hollow portion having a desired shape can be surely liquid-tightly sealed, more preferably hermetically sealed.

  In the present embodiment, as described above, the first support layer 17 is formed to have a closed shape along the outer peripheral edge of the piezoelectric substrate 2. Therefore, in the second support layer 18, the dimension in the thickness direction connecting the inner wall and the outer wall is relatively small. On the other hand, the second support layer 18 is provided on the inner side of the first support layer 17 through the hollow path 19, but has a relatively large area. But the 2nd support layer 18 has an area smaller than the support layer 102 of the elastic wave apparatus 101 of the comparative example shown in FIG.

  In the step of bonding the cover member 20 onto the support layer 16 by roller pressure bonding, voids are more likely to occur as the area of the bonded portion increases. Therefore, in the acoustic wave device 101 shown in FIG. 5, a void as shown by an arrow B may occur so as to connect between the hollow portion and the outside. For this reason, a leak failure tends to occur.

  On the other hand, in the elastic wave device 1 of the present embodiment, even if a void reaching the hollow portion occurs in the second support layer 18, the other end of this void does not communicate with the outside air, It will remain in the part leading to the path 19. Therefore, a leak failure between the hollow portion and the outside can be reliably suppressed.

  The area of the support layer of the second support layer 18 is large and voids are likely to occur. However, since the hollow path 19 is provided, the voids of the support layer 18 are not a problem.

  As described above, in the acoustic wave device 1 of the present embodiment, it is possible to reliably suppress fluctuations in frequency characteristics and a decrease in moisture resistance due to a leak failure.

  FIG. 4 is a schematic plan view of an acoustic wave device according to the second embodiment of the present invention. Also in FIG. 4, illustration of the cover member is omitted. That is, the elastic wave device 21 with the cover member removed is shown. In the acoustic wave device 21, the support layer 24 includes the first support layer 17 and the second support layer 26. The elastic wave device 21 is configured in the same manner as the elastic wave device 1 except that the second support layer 26 is different from the second support layer 18. Therefore, the same reference numerals are assigned to the same parts, and the description of the first embodiment is incorporated.

  In the acoustic wave device 21, the second support layer 26 is formed of the same material as the first support layer 17, but the second support layer 26 further includes a plurality of openings 26 a and 26 b. The openings 26 a and 26 b are provided in the second support layer 26. Accordingly, the area of the second support layer 26 is smaller than the area of the second support layer 18 of the first embodiment.

  Therefore, in the step of laminating the cover member 20 (FIG. 2) on the first and second support layers 17 and 26, voids are less likely to occur between the second support layer 26 and the cover member. Even if a void reaching the openings 26a and 26b is formed, that is, even if a void extending from the inner hollow portion to the second hollow portion is generated, the void does not reach the outside. That is, since the air mass mixed in the joint surface between the support layer 16 and the cover member 20 can be discharged to the hollow path 19 disposed in the vicinity of the peripheral edge of the support layer 16, generation of voids is suppressed. can do. Therefore, the occurrence of a leak failure can be more effectively prevented.

  Thus, in the present invention, one or more openings may be appropriately formed in the second support layer.

  In the first and second embodiments, the first support layer 17 has a closed loop shape along the outer peripheral edge of the piezoelectric substrate 2. Thus, it is desirable that the first support layer 17 has a closed loop shape, thereby further improving the sealing performance in the acoustic wave device. However, the first support layer may be partially cut away.

  In the first embodiment, one hollow passage 19 is provided so as to communicate a plurality of hollow portions, but the hollow passage 19 is disposed so as to communicate at least two hollow portions. There is no particular limitation.

  Furthermore, a plurality of hollow paths may be provided.

  Further, the configuration of the plurality of acoustic wave element portions in the acoustic wave device of the present invention is not limited to the configuration of the above embodiment. In other words, the present invention can be applied to an appropriate acoustic wave device in which a plurality of acoustic wave element portions including acoustic wave resonators and acoustic wave filters are configured on a piezoelectric substrate.

DESCRIPTION OF SYMBOLS 1 ... Elastic wave apparatus 2 ... Piezoelectric substrate 3 ... Antenna terminal 4 ... Common terminal 5 ... Transmission terminal 6a, 6b ... Balance terminal 7 ... Transmission filter 8 ... Reception filter 9 ... 1 port type | mold elastic wave resonator 11 ... IDT electrode 12, DESCRIPTION OF SYMBOLS 13 ... Reflector 14, 15 ... Elastic wave filter part 16 ... Support layer 17 ... 1st support layer 17a ... Main body part 17b ... Via conductor formation part 18 ... 2nd support layer 19 ... Hollow path 20 ... Cover member 21 ... Elastic wave device 24 ... support layer 26 ... second support layers 26a, 26b ... opening 31 ... IDT electrodes P1-P4 ... parallel arm resonators S1-S4 ... series arm resonators

Claims (5)

A piezoelectric substrate;
A plurality of acoustic wave element portions provided on the piezoelectric substrate and having at least one IDT electrode;
A support layer disposed on the piezoelectric substrate outside the region where the acoustic wave element portion is provided in order to form a hollow portion in each portion where the acoustic wave element portion is provided;
A cover member laminated on the support layer in order to seal each portion provided with the acoustic wave element portion and form the hollow portion;
A first support layer disposed so that the support layer extends along an outer peripheral edge of the piezoelectric substrate;
A second support layer disposed in a region surrounded by the first support layer, the second support layer being provided so as to surround a portion where the acoustic wave element unit is provided in the region; Have
An acoustic wave device in which a hollow path is provided between the first support layer and the second support layer, and the hollow path is disposed so as to communicate with at least two of the hollow portions. .   The acoustic wave device according to claim 1, wherein an opening is provided in the second support layer so as to reduce a plane area of the second support layer.   The elastic wave device according to claim 1 or 2, wherein the first support layer has a closed loop shape. Before SL during the air portion are sealed liquid-tight, elastic wave device according to any one of claims 1 to 3.   3. The acoustic wave device according to claim 1, wherein when viewed in a plan view, an outer peripheral edge of the cover member reaches an outer peripheral edge of the piezoelectric substrate to constitute a wafer level package.

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